plastic-intent-continuing

Use when a specific intent is named to resume, by id or by description, or on continuing --intent {id}. Reads that intent's savepoint ledger and hands off to plastic-intent-starting. The general "continue" / new-session triggers belong to the plastic-continuing router, not here, so a bare "continue" does not settle on this skill directly. Boot (health check, core context, version, statusline) is owned by the…